Manufacture of photographic pictures



I Patented June 22, 1937 MANUFACTURE OF PHOTOGRAPHIC PICTURES lldith Weyde, Cologne-Nicki, Germany, assignor to Agfa Ansco Corporation, Blnghamton, N. Y., a corporation of New York 'No Drawing. Application July 25, 1934, Serial No. 736,959. In Germany July 25 1933 My present invention relates to the manufacture of photographic pictures.

One of its objects is a process of producing photographic pictures. Further objects will'be seen from the detailed specification following hereafter.

There are two fundamentally different'processes for producing photographic pictures name- 1y a printing process and a developing process. In the printing process, the whole of the substance forming the picture is produced by the light itself, while in the developing process only' a very small part of the sensitive material used is decomposed by the light and a latent, or very l5 faintly visible, image is obtained from which the full image is produced by a subsequent chemical process. For. the developing process it has hithcrto been possible to use only noble metal salts (Ag, Hg), in which the metal in question is formed'as a nucleus.

The present invention relates to a process of producing metal sulfide pictures by means of a developing method, wherein the sensitivity of the rinting surface to light much exceeds that of the surfaces used in the known developing processes and corresponds with that of the silver halide developing papers.

' One method of producing metal sulfide pictures by a developing process is as follows:Certain heavy metal compounds of substances containing sulfur which in light are decomposed into the corresponding metal sulfides, are also affected in the same manner as by the light by different reagents, for instance, alkalies or acids, and it has been found that this action is accelerated by small proportions of the metal sul-' fides in question. Accordingly, metal-sulfide produced in traces by exposure to light acts as nuclei similarly to metallic silver in the ordinary ess all metals are suitable which yield darkmetal sulfides, such as, for instance, lead, copper, bismuth, silver, mercury, thallium, molybdenum, tungsten, uranium, cobalt and nickel. As sulfur compounds in the sensitive layer and in the developer there may be used those. which yield metal sulfides comparatively easily, such as, for

' example, thiolirea and derivatives thereof, thioamides or thioacids. For developing there may be used alkaline baths which contain a substance capable of convertingthe metal compound into a sulfide; in certain cases, however, an acid I development is possible. It is often not necessary to start with the metal compound of a sulfur compound. In most cases it is preferable to use a mixture of the sulfur compound and a metal combined otherwise than with the said sulfur compound. In this case it is advantageous that only a small proportion of .the sulfur compound should be added to the sensitive layer itself (sufficient for the formation of metal sulfide nuclei), the main part being added 'to the developer.

. However, with certain compounds, such as complex compounds of cobalt, nickel or copper, it is unnecessary to add any sulfur compound to the sensitive layer since the sulfide nuclei can be formed in the developing bath. In these layers there are produced at the parts exposed to light ionizable metal compounds.

As sensitive material in this case there are suitable the various metal complex salts, for instance, of cobalt, nickel or copper with nitrates, oxalates, organic amines and phenolates which .are so changed by light that compounds containing the metal in ionizable combination are produced. Many metal complexes react only relatively slowly with sulfur compounds, but very quickly when even only very small proportions of the metal ion in question are present. The metal ions are presumably converted very quickly into metal sulfide and act asnuclei for the further formation of sulfide from the complex compound. It is in this case advantageous not to use sodium sulfide as developer but a compound in which the reactivity of the sulfide-ion is somewhat more tardy, for example a polysulfide, or a sulfa-salt. Thus it is possible, for instance, to develop the latent image in a layer containing the salt (Co(NI-Ia) (N02) :CzOI.) NH4 as sensitive substance,

by means of a sodium polysulflde solution. The following experiment shows that this is actually a development, not merely a conversion of the light-decomposition product into sulfide. If one writes on a, pure g'elatine' layer with a cobalt chloride solution of 0.001 per cent-strength, the written characters cannot be rendered visible by a subsequent treatment with a sodium-polysul- 'fide solution in consequence of the excessively small concentration of cobal salt; if, however, the gelatine layer contains from the outset some'of the complex salt ofthe above formula the writing in cobalt chloride becomes very prominent on treatment with sodium polysulfide as in this case the extremely small quantity of cobalt chloride determines formation of cobaltsulfide from the complex compound.

" tion.

Y The process a; not to the ahoveenientioned cobalt complexsalt, but'for the purpose there is suitable'a verylarge number-of compounds which on the one hand are sufliciently" sensitive to; light and on-the other hand yield dark sulfides, such as nickel, iron, copper or like compounds.

As already briefly explained above, suitable developersare principally sulfideswhich in conse- .quence of formation of polysulfide or sulfo-salt Y are less'reactivethan pure sulfides. As developers theremay also be used mixtures of substances which react only relatively slowly with the formation of free sulfide-ion, such as, for example, a' solution of thioacetamide and caustic soda soluvThe light-sensitive substances which come un- ,der consideration are further characterized in that in a number of them the latent image, which can be developed, can be produced not only by the energy of the light rays, but, for instance,

' with nickel complex compounds by that of heat rays for, forinstance, with lead compounds by j that of x-rays or by that of electric currents.

The following examples illustrate the invention: v y Y Example 1.'-30 cc. of a lead nitrate solution of -10 per cent strength are mixed with .10 cc. of

gum arabic solution (10 per cent) and the" mixture is.precipitated by adding 33 cc. of potassium iodide solutionof 10 per cent strength. To the very fine suspension alcohol is added, and the settled precipitate is washed several times with alcohol containing wateran'd then freed as far as'possible from alcohol by filtration. The resi-' due on the fllter is dissolved in cc. of water and mixed with .100 cc. of gelatine solution of 10 per cent strength, 1 gram of thioacetamide and 10 cc. of glycerine. The finished emulsion is cast in known manner. Thus a very highly light-sen- .sitive'material is obtained which also reacts to Rontgen-rays whose latent image can bel-de- V veloped by the following developer mo cc..- 1,000

Thioacetamide grams 10' NaOH grams 3 The time of developing amounts .to about 1 to '3 minutes. After the development, the picture is preferably treated with a dilute sodium thiosulfate solution.

Example z. 2 grams of tcomnmmoamnm which has been purified by recrystallizing several times very carefully, are dissolved. in 100 .cc. of water and, at a maximum temperature of 40' 0., are mixed with '50 cc. of gelatine solution of 10 per cent strength. A latent imagefcan be produced in a layer obtained from this solution by light or by an electric current. "Hie latent image isdeveloped by a solution of the following composition:

In a solution of 5 gramsof ammonium sulfide in cc. of water, 1 8mm, of sulfur is dissolved by boiling. For use, this solution is diluted with 1Q times its volume of water. a 1

The duration of devolopment amounts to 1 to' -2=m'inutes; the picture 'is'flxed by washing with water. In this manner deep brown pictures are obtained.

What I claim is:

1. Aprocess or photographic pic tures which comprises exposing to light an emulsion layer containing a compound of a heavy metal capable of forming a darkecolored sul- .;a,oe4,4so I A ,jflde until developable nuclei are formed, and treating the latentimage thus produced with a solution containing a thin-compound capable of forming the metal sulfide to form a visible imagefrom' the latent image immediately follow-' 2. A. process or producing photographic pictures'which comprises exposing to light an emulsion layer containing a complex compound of a heavy metal, said complex compound being capable to form under the action of light a com-1 pound which contains the metaiin ionizable link age until developabie nuclei are formed, and

treatingthe latent image thus obtained with a solution -containing a thio-compound capable of .forming the metal sulfide to form a visible image from the latent image immediately following exposure.

3., A process of producing photographic pictures-which comprises exposing to light an emulsion layer'containing a compound of a heavy metal selected from the group consisting of lead,

.copper, bismuth, silver, mercury, thallium, mo-

lybdenum, tungsten, uranium, cobalt and nickel until developabie nuclei are formed, and treating the latent image thus produced with a solution. containing a thio-compound capable of forming the metal sulfide to form a visible image from the latent image immediately following exposure. 4. A process of producing photographic pictures which comprises exposing to light an emulsion layer containing a complex compound of a heavy metal selected from the group consisting of cobalt, nickel and copper with a compound selected from 'the group consisting of nitrates, oxalates, amines and phenolates'until developable nuclei are formed, and treatingthe latent image thus formed with a solution containing a thio-compound capable of forming the metal sulfide to form a visible image from the latent image immediately following 5. A process of producing photographic pictures which comprises exposing to light an emulsion layer containing (Co(NH:)a(NO:) 4) NH; until deveiopable nuclei are formed and treating the latent image'thus obtained in an aqueous s'olution of ammonium-polysulfide to form a visible image from the latent image immediately following exposure.

6. A process of producing photographic pic-. tures which comprises exposing to light an emulsion layer containing a compound of a heavy metal capable of forming a dark-colored sulfide and a thic-compound capable of forming the.

metal-sulfide, until developable nucleiare" formed, and treating the latent image thus produoed with a solution containing a thio compound cap'ableof forming the metal-sulfide, to form a visible image from the'latent image immediately following exposure. 7 ['L'A process of producing photographic piccopper, bismuth, silver, mercury, thallium, molybdenum, tungsten, uranium, cobalt and nickel and j tures which comprlsesexposlng to light an emul-' sion layer containing. a compound of a heavy "metal selected from the group consisting of lead,

a thin-compound capable offormin'g the metal-' suinde, until developable nuclei are formed, and

treating the latent image thus produced with a 1 I solution containing a thio-compound capable of forming the metal sulfideto fonn a visible image from the latent image follqwiug 

